1. Field of the Invention
The present invention relates to a thin-film magnetic head having at least a magnetoresistive element for reading and a method of manufacturing such a thin-film magnetic head, and to a magnetoresistive device having a magnetoresistive element.
2. Description of the Related Art
Performance improvements in thin-film magnetic heads have been sought as surface recording density of hard disk drives has increased. Composite thin-film magnetic heads have been widely used. A composite head is made of a layered structure including a recording head having an induction-type magnetic transducer for writing and a reproducing head having a magnetoresistive (MR) element for reading. MR elements include an anisotropic magnetoresistive (AMR) element that utilizes the AMR effect and a giant magnetoresistive (GMR) element that utilizes the GMR effect. A reproducing head using an AMR element is called an AMR head or simply an MR head. A reproducing head using a GMR element is called a GMR head. An AMR head is used as a reproducing head whose surface recording density is more than 1 gigabit per square inch. A GMR head is used as a reproducing head whose surface recording density is more than 3 gigabits per square inch.
Many of reproducing heads have a structure in which the MR element is electrically and magnetically shielded by a magnetic material.
Reference is now made to FIG. 14A to FIG. 19A and FIG. 14B to FIG. 19B to describe an example of a manufacturing method of a composite thin-film magnetic head as an example of a related-art manufacturing method of a thin-film magnetic head. FIG. 1 to FIG. 19A are cross sections each orthogonal to the air bearing surface of the head. FIG. 14B to FIG. 19B are cross sections each parallel to the air bearing surface of the pole portion of the head.
According to the manufacturing method, as shown in FIG. 14A and FIG. 14B, an insulating layer 102 made of alumina (Al2O3), for example, having a thickness of about 5 to 10 xcexcm is deposited on a substrate 101 made of aluminum oxide and titanium carbide (Al2O3-TiC), for example. On the insulating layer 102 a bottom shield layer 103 made of a magnetic material and having a thickness of 2 to 3 xcexcm is formed for a reproducing head.
Next, on the bottom shield layer 103, a first bottom shield gap film 104a as an insulating layer made of alumina, for example, is deposited to a thickness of 40 to 70 nm, for example. On the first bottom shield gap film 104a, an MR film having a thickness of tens of nanometers is formed for making an MR element 105 for reproduction. Next, on the MR film a photoresist pattern 106 is selectively formed where the MR element 105 is to be formed. The photoresist pattern 106 is formed into a shape that facilitates lift-off, such as a shape having a T-shaped cross section. Next, with the photoresist pattern 106 as a mask, the MR film is etched through ion milling, for example, to form the MR element 105. The MR element 105 may be either a GMR element or an AMR element.
Next, as shown in FIG. 15A and FIG. 15B, a second bottom shield gap film 104b as an insulating layer is formed in a region on top of the first bottom shield gap film 104a except the neighborhood of the MR element 105. The second bottom shield gap film 104b is made of alumina, for example, and has a thickness of 100 to 200 nm, for example. Next, using the photoresist pattern 106 as a mask, a pair of first conductive layers (that may be called leads) 107 whose thickness is 50 to 100 nm, for example, are formed into specific patterns on the first bottom shield gap film 104a and the second bottom shield gap film 104b. The first conductive layers 107 are electrically connected to the MR element 105 and may be made of copper (Cu), for example.
Next, as shown in FIG. 16A and FIG. 16B, the photoresist pattern 106 is lifted off. Next, a first top shield gap film 108a made of alumina, for example, and having a thickness of 40 to 70 nm, for example, is formed as an insulating layer on the bottom shield gap films 104a and 104b, the MR element 105 and the first conductive layers 107. The MR element 105 is embedded in the shield gap films 104a and 108a. Next, a second top shield gap film 108b as an insulating layer is formed in a region on top of the first top shield gap film 108a except the neighborhood of the MR element 105. The second top shield gap film 108b is made of alumina, for example, and has a thickness of 100 to 200 nm, for example.
Next, as shown in FIG. 17A and FIG. 17B, contact holes 130 are formed through selectively etching portions of the top shield gap films 108a and 108b located on top of an end of each of the first conductive layers 107 opposite to the MR element 105 (that is, on the right side of FIG. 17A). The first conductive layers 107 are thus exposed.
Next, as shown in FIG. 18A and FIG. 18B, on the top shield gap films 108a and 108b, a top-shield-layer-cum-bottom-pole-layer (called a top shield layer in the following description) 109 having a thickness of about 3 xcexcm is formed. The top shield layer 109 is made of a magnetic material and used for both a reproducing head and a recording head. At the same time, a pair of second conductive layers 110 having a thickness of about 3 xcexcm are formed on the bottoms of the contact holes 130 (FIG. 17A). The second conductive layers 110 are made of the same material as the top shield layer 109 and electrically connected to the first conductive layers 107. Next, an insulating layer 112 made of alumina, for example, and having a thickness of 4 to 6 xcexcm, for example, is formed over the entire surface. The insulating layer 112 is flattened through chemical mechanical polishing (CMP), for example, until the top shield layer 109 and the second conductive layers 110 are exposed, and the surface is flattened.
Next, as shown in FIG. 19A and FIG. 19B, on the top shield layer 109, a recording gap layer 113 made of an insulating film such as an alumina film whose thickness is 0.2 to 0.3 xcexcm is formed. Contact holes are formed through selectively etching a portion of the recording gap layer 113 in a center region where a thin-film coil described later is formed and portions on top of the second conductive layers 110. Next, third conductive layers 114 connected to the second conductive layers 110 are formed in the contact holes provided on top of the second conductive layers 110.
Next, on the recording gap layer 113, a photoresist layer 115 for determining the throat height is formed into a specific pattern whose thickness is about 1.0 to 2.0 xcexcm. The throat height is the length (height) of portions of the two magnetic layers of the recording head between the air-bearing-surface-side end and the other end, the portions facing each other with the recording gap layer in between.
Next, on the photoresist layer 115, the thin-film coil 116 of the recording head is formed. The thickness of the coil 116 is 3 xcexcm, for example. Next, a photoresist layer 117 is formed into a specific pattern on the photoresist layer 115, the coil 116 and the third conductive layers 114.
Next, a top pole layer 118 having a thickness of about 3 xcexcm is formed for the recording head on the recording gap layer 113 and the photoresist layers 115 and 117. The top pole layer 118 is made of a magnetic material such as Permalloy (NiFe) and is in contact with and magnetically coupled to the top shield layer (bottom pole layer) 109 through the contact hole formed in the center portion of the region where the thin-film coil 116 is formed.
Next, the recording gap layer 113 and the top shield layer (bottom pole layer) 109 are etched through ion milling, for example, using the top pole layer 118 as a mask. As shown in FIG. 19B, the structure is called a trim structure wherein the sidewalls of the top pole layer 118, the recording gap layer 113, and part of the top shield layer (bottom pole layer) 109 are formed vertically in a self-aligned manner. The trim structure suppresses an increase in the effective track width due to expansion of the magnetic flux generated during writing in a narrow track.
Next, an overcoat layer 119 of alumina, for example, having a thickness of 20 to 30 xcexcm is formed to cover the top pole layer 118. The surface of the overcoat layer 119 is flattened and pads for electrodes not shown are formed on the surface of the overcoat layer 119. Finally, machine processing (lapping) of the slider is performed to form the air bearing surfaces of the recording head and the reproducing head. The thin-film magnetic head is thus completed.
As the performance of a reproducing head improves, a problem of thermal asperity comes up. Thermal asperity is a reduction in reproducing characteristics due to self-heating of the reproducing head during reproduction. To overcome such thermal asperity, the thickness of each shield gap film has been reduced down to 40 to 70 nm, for example, in order to increase the cooling efficiency.
However, such thin shield gap films cause a problem that faults may result in the magnetic and electrical insulation that isolates the shield layers from the MR element or the first conductive layers connected thereto.
In relation to this problem, another problem of the prior-art thin-film magnetic head is a short circuit between the shield layers and the MR element or the first conductive layers connected thereto. This problem will now be described, referring to the example shown in FIG. 14A to FIG. 19A and FIG. 14B to FIG. 19B.
In the method of manufacturing the thin-film magnetic head of the related art, the top shield layer 109 and the second conductive layers 110 as shown in FIG. 18A and FIG. 18B are formed through plating, for example. In this case, before forming the plating layers of the top shield layer 109 and the second conductive layers 110, a seed layer required for growing the plating layers is formed through sputtering.
The second conductive layers 110 are electrically connected to the first conductive layers 107 through the contact holes 130 shown in FIG. 17A. Therefore, the ohmic resistance between the second conductive layers 110 and the first conductive layers 107 is required to be low. In order to achieve this through the related-art method, oxides on the surfaces of the first conductive layers 107 are removed through reverse sputtering before forming the seed layer on the first conductive layers 107. The ohmic resistance on the surfaces of the first conductive layers 107 is thereby reduced.
In the related art, however, portions of the top shield gap films 108a and 108b near the MR element 105 may be etched or suffer plasma-induced damage because of the reverse sputtering mentioned above. Holes are thus formed in the top shield gap films 108a and 108b in some cases. FIG. 20 illustrates the state in which the top shield gap films 108a and 108b have holes 140 near the MR element 105.
If the top shield layer 109 is formed while the top shield gap films 108a and 108b have the holes 140, a short circuit is created between the top shield layer 109 and the MR element 105 or the first conductive layers 107, as shown in FIG. 21. Such a short circuit results in an increase in noise that affects the MR element 105.
It is an object of the invention to provide a thin-film magnetic head and a method of manufacturing the same and a magnetoresistive device for preventing a short circuit between a shield layer and a magnetoresistive element or a first conductive layer connected thereto.
A thin-film magnetic head of the invention comprises: a magnetoresistive element; two shield layers, placed to face each other with the magnetoresistive element in between, for shielding the magnetoresistive element; a first conductive layer connected to the magnetoresistive element; two insulating layers each of which is provided between each of the shield layers and the magnetoresistive element and the first conductive layer, one of the insulating layers having a contact hole; and a second conductive layer connected to the first conductive layer through the contact hole of the one of the insulating layers. One of the shield layers located closer to the one of the insulating layers than the other one of the shield layers includes: a first layer touching the one of the insulating layers; and a second layer made of a material the same as a material of which the second conductive layer is made.
According to the thin-film magnetic head of the invention, the first layer of the one of the shield layers is provided to touch the one of the insulating layers having the contact hole. As a result, the one of the insulating layers is protected by the first layer of the one of the shield layers when the second conductive layer made of the same material as that of the second layer of the one of the shield layers is formed.
The thin-film magnetic head of the invention may further comprise a base layer that is a base of the second conductive layer and made of a material the same as a material of which the first layer of the one of the shield layers is made. In this case, the contact hole penetrates the base layer and the one of the insulating layers.
The thin-film magnetic head may further comprise an induction-type magnetic transducer for writing including: two magnetic layers magnetically coupled to each other and including magnetic pole portions opposed to each other, the pole portions being located in regions on a side of a surface facing a recording medium, the magnetic layers each including at least one layer; a gap layer placed between the pole portions of the magnetic layers; and a thin-film coil at least part of which is placed between the magnetic layers, the at least part of the coil being insulated from the magnetic layers. In this case, the one of the shield layers may function as one of the magnetic layers, too.
A method of the invention is provided for manufacturing a thin-film magnetic head comprising: a magnetoresistive element; a first shield layer and a second shield layer, placed to face each other with the magnetoresistive element in between, for shielding the magnetoresistive element; a first conductive layer connected to the magnetoresistive element; a first insulating layer provided between the first shield layer and the magnetoresistive element and the first conductive layer; a second insulating layer provided between the second shield layer and the magnetoresistive element and the first conductive layer, the second insulating layer having a contact hole; and a second conductive layer connected to the first conductive layer through the contact hole of the second insulating layer. The method includes the steps of: forming the first shield layer; forming the first insulating layer on the first shield layer; forming the magnetoresistive element on the first insulating layer; forming the first conductive layer on the first insulating layer; forming the second insulating layer on the magnetoresistive element, the first conductive layer and the first insulating layer; forming a first layer of the second shield layer on the second insulating layer; forming the contact hole in a portion of the second insulating layer that connects the first conductive layer to the second conductive layer after the step of forming the first layer of the second shield layer; forming a second layer of the second shield layer on the first layer of the second shield layer; and forming the second conductive layer to be connected to the first conductive layer through the contact hole.
According to the method of the invention, the contact hole is formed in the portion of the second insulating layer that connects the first conductive layer to the second conductive layer after the first layer of the second shield layer is formed on the second insulating layer. As a result, the second insulating layer is protected by the first layer of the second shield layer when the second conductive layer is formed.
According to the method, the second conductive layer may be formed through plating in the step of forming the second conductive layer.
The method may further include the step of performing processing of reducing an ohmic resistance of a portion of the first conductive layer to be connected to the second conductive layer prior to the step of forming the second conductive layer.
According to the method, the step of forming the second conductive layer may be performed at the same time as the step of forming the second layer of the second shield layer, and the second conductive layer may be made of a material the same as a material of which the second layer of the second shield layer is made.
According to the method, a base layer may be formed on a portion of the second insulating layer where the contact hole is to be formed at the same time as the step of forming the first layer of the second shield layer. The base layer is a base of the second conductive layer and made of a material the same as a material of which the first layer of the second shield layers is made. In this case, the contact hole is formed to penetrate the base layer and the second insulating layer in the step of forming the contact hole.
The method may further include the step of forming an induction-type magnetic transducer for writing including: two magnetic layers magnetically coupled to each other and including magnetic pole portions opposed to each other, the pole portions being located in regions on a side of a surface facing a recording medium, the magnetic layers each including at least one layer; a gap layer placed between the pole portions of the magnetic layers; and a thin-film coil at least part of which is placed between the magnetic layers, the at least part of the coil being insulated from the magnetic layers. In this case, the second shield layer may function as one of the magnetic layers, too.
A magnetoresistive device of the invention comprises: a magnetoresistive element; two shield layers, placed to face each other with the magnetoresistive element in between, for shielding the magnetoresistive element; a first conductive layer connected to the magnetoresistive element; two insulating layers each of which is provided between each of the shield layers and the magnetoresistive element and the first conductive layer, one of the insulating layers having a contact hole; and a second conductive layer connected to the first conductive layer through the contact hole of the one of the insulating layers. One of the shield layers located closer to the one of the insulating layers than the other one of the shield layers includes: a first layer touching the one of the insulating layers; and a second layer made of a material the same as a material of which the second conductive layer is made.
According to the magnetoresistive device of the invention, the first layer of the one of the shield layers is provided to touch the one of the insulating layers having the contact hole. As a result, the one of the insulating layers is protected by the first layer of the one of the shield layers when the second conductive layer made of the same material as that of the second layer of the one of the shield layers is formed.
The magnetoresistive device of the invention may further comprise a base layer that is a base of the second conductive layer and made of a material the same as a material of which the first layer of the one of the shield layers is made. In this case, the contact hole penetrates the base layer and the one of the insulating layers.
Other and further objects, features and advantages of the invention will appear more fully from the following description.